Question: A bag contains $4$ red marbles, $6$ green marbles, and $7$ blue marbles. If a marble is randomly chosen, what is the probability that it is not red?
Answer: There are $4 + 6 + 7 = 17$ marbles in the bag. There are $4$ red marbles. That means $17 - 4 = 13$ are not red. The probability is $ \frac{13}{17}$.